When converting signals from a digital to an analog format dither is often added to reduce the effect of non-linearity in the Digital-to-Analog converter (DAC). In particular, as digital codes are input to the DAC, the analog output voltage may be skewed to an incorrect value. If a digital signal periodically uses a code which produces a skewed output voltage, then the output signal will be distorted. With dither added to the digital signal, each time the code would normally be used that produced a skewed output voltage, the dither perturbs the signal so that other digital codes are used instead. When this happens over many periods, an averaging effect takes place, resulting in a more correct output voltage. For small amounts of non-linearity, a small dither signal is sufficient. However, for effective dithering in segmented DACS, the dither noise signal must be large enough to average out the effects of crossing the segment boundaries.
Likewise, when converting signals from an analog to a digital format distortion results when the digital output codes correspond to incorrect analog input voltages. This distortion can be reduced by injecting an analog dither signal onto the analog signal prior to conversion to a digital format. In a manner similar to DACs described in the previous paragraph, analog dither must be of a magnitude to average out the effects crossing segment boundaries in a segmented analog-to-digital converter (ADC).
In both cases of digital-to-analog and analog-to-digital conversion of a signal, the dither signal may need to be eliminated from the converted signal in order to maintain signal quality. Therefore a need exists for a method and apparatus for the addition and removal of a dither signal from the converted signal.